1. Field of the Invention
The present invention relates to integrally molded polyurethane foam products (designated hereafter as integrally molded urethane products) that are obtained by integrally molding skin materials and polyurethane foam materials (designated hereafter as foam materials) and to the method of producing the products. The integrally molded urethane products of the present invention are used for manufacturing head-rest, arm-rest, center arm-rest and other cushion products for car.
2. Prior Art
Conventionally such head-rest and other cushion products for car have been manufactured by integrally foaming or pouring in place (hereinafter described as "foam in place") in which a foaming material such as reactive foam ingredients of polyurethane foam is deposited on or into a skin member to be covered and the foaming reaction takes place in it. However, for the skin member for a covering using a fabric with high permeability of gases or liquid, such a two (2) or three layered skin member has hitherto been employed. The former is a laminated fabric made by laminating a fabric and a synthetic resin film (designated sometimes hereafter simply as film), that has virtually no gas premeability and the latter is another laminated one made by sandwiching a polyurethane slab-foam layer between the laminated fabric. An example of a method for producing a heat-rest using such a two(2) layered, laminated fabric is shown in FIG. 5, in which the numeral 50 stands for a foaming mold comprising several mold parts, 51 for product cavity, 52 for an insert and P for a liquid foaming material of polyurethane, and in the cavity 51 is placed a covering 53 that has been formed into a desired shape by cutting and sewing skin members. The numeral 55 stands for the seams.
From these description it is clear that the 2 previous skin members have the following problems.
(i) As the above film, polyurethane film, polyvinyl chloride film and other films have been used conveniently, but the surface of these films have so low sliding properties because of its sticky characteristic that the sewing movement of a sewing machine is not smooth causing insufficient sewing performance. To make sewing smoother silicone oil has usually been applied over the film surface, but due to the high releasing action of silicone oil the skin member and polyurethane foam (sometimes designated hereafter simply as foam) tend to separate readily.
(ii) When gas evolves in the course of foaming of a foaming material, it remains as bubbles between the film and the foam because there is no exit for gas.
(iii) Due to no gas permeability of the film, the foaming pressure of the foaming material concentrates to seams of the skin member resulting in exudation and stain of the foaming material therefrom. Accordingly an operation to remove the exuded foam is required after removing the product from the die.
(iv) Due to no gas permeability around surface of the molded product, it gives stuffy and other unpleasant feelings to touch.
(v) Because a film with relatively high rigidity is joined over the surface of a foam, flexibility of the surface of a molded product is impaired giving a rigid touch unless a polyurethane slab-foam layer is specially provided.
(vi) For increasing gas permeability and flexibility around surface of the foam, which is in contact with the skin member, such an after-treatment as roll crushing or piercing crushing is required after removing molded product. For example, a method of such an after-treatment is shown in FIG. 6. Thus, the sign M in FIG. 6 stands for a molded product and 60 for a piercing apparatus. The inner surface of the latter is made to fit the outer form of the molded product M, and is provided with numerous needles 61 that can reach the plastic film 56 so that the film is pressed from outside through the molded product M. In addition to this procedure, compressing the pierced molded product M with a roller, or the so-called process of crushing, may be sometimes employed in combination.
In this way an additional process is required causing rise in equipment cost and man-hour. For the so-called doughnut-form head-rest that is molded into a round form (or doughnut form), even the above piercing apparatus 60 cannot make holes to the film in the skin member that constitutes the inner surface of the doughnut ring. Subsequently gas permeability in these parts becomes poor causing stuffy touch when the head rest is used.